Patents Assigned to NTT Mobile Communication Network Inc.
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Patent number: 5721742Abstract: A transmittal signal is transmitted in a forward error correction format in case the length of the transmittal signal satisfies predetermined conditions but not in a forward error correction format in case the length of the transmittal signal does not satisfy the predetermined conditions. Owing to this arrangement, a long signal susceptible to errors, can be encoded in a forward error correction format. For transmitting a short transmittal signal, wasteful consumption of transmission data capacity of a radio channel can be prevented.Type: GrantFiled: May 1, 1996Date of Patent: February 24, 1998Assignee: NTT Mobile Communications Network Inc.Inventors: Ichiro Okajima, Akihiro Maebara, Shoichi Hirata, Katsumi Kobayashi
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Patent number: 5715235Abstract: A communication apparatus is disclosed which is capable of measuring levels of carrier signals used in adjacent zones during telecommunication with a small circuit scale, and capable of simultaneously transmitting/receiving to FDMA-system signals through a plurality of communication channels. All of transmission signals received through the communication channels under use are wholly converted into an intermediate signal by a mixer. The intermediate signal is quadrature-detected and then A/D-converted into digital I/Q-channel signals by A/D-converters. Thereafter, the digital I/Q-channel signals are frequency-converted by frequency converting circuits in such a manner that center frequencies of these I/Q-channel signals become zero, two sets of I/Q-channel signals may be demodulated by two sets of demodulating circuits. Otherwise, one of these I/Q-channel signals is demodulated by a single demodulating circuit, and the other is level-detected by a level detecting circuit.Type: GrantFiled: November 21, 1994Date of Patent: February 3, 1998Assignee: NTT Mobile Communications Network Inc.Inventors: Mamoru Sawahashi, Tomohiro Dohi, Fumiyuki Adachi
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Patent number: 5715525Abstract: Band-pass filters BPF1, BPF2, and BPF3 correspond to the reception frequency band for FDD, the transmission band for FDD, and the band for TDD, respectively. An antenna A1 is used in common for transmission and reception in the FDD and TDD systems. Another antenna A2 is used for diversity reception in the FDD system. A controller 20 controls switches SW1 through SW4. When the FDD system is selected, the reception signal is sent from the antenna A1 or A2 through the filter BPF1 to a reception amplifier RA, and the transmission signal is sent from the transmission amplifier TA through the filter BPF2 to the antenna A1. When the TDD system is selected, the reception signal is sent from the antenna A1 through the filter BPF3 to the reception amplifier RA, and the transmission signal is sent from the transmission amplifier TA through the filter BPF3 to the antenna A1.Type: GrantFiled: June 26, 1996Date of Patent: February 3, 1998Assignee: NTT Mobile Communications Network Inc.Inventors: Yoshiaki Tarusawa, Toshio Nojima
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Patent number: 5710792Abstract: A baseband signal, obtained by quasi-coherent detecting a received signal, is sampled and written as a sequence of baseband signal samples into a buffer memory. For each baseband signal sample read out from the buffer memory, a maximum likelihood sequence estimation part generates a desired symbol sequence and feeds it to a transversal filter having a characteristic based on an estimated impulse response of the transmission path in correspondence with the timing of the baseband signal sample. A phase error between an estimated received signal from the transversal filter and the corresponding baseband signal sample is sequentially detected by a phase error detecting part. The phase error thus obtained is fed to an offset correcting signal generating part, which calculates an estimated offset angular frequency .DELTA..omega..sub.Type: GrantFiled: April 17, 1995Date of Patent: January 20, 1998Assignee: NTT Mobile Communications Network, Inc.Inventors: Kazuhiko Fukawa, Hitoshi Yoshino, Hiroshi Suzuki
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Patent number: 5703941Abstract: A switching center 30 comprises a memory part M2, a memory part M3, and a memory part M4. The memory part M2 stores a terminating terminal number corresponding to and registered by each subscriber. The memory part M3 stores idle/busy information corresponding to each terminal. The memory part M4 stores idle/busy information corresponding to each subscriber. When a subscriber 11.sub.1 makes a call at a terminal 12.sub.2, the switching center 30 determines whether the idle/busy information for the subscriber 11.sub.1 stored in the memory part M4 is idle or busy. When the idle/memory information represents idle, the switching center 30 refers to the idle/busy information for the terminal 12.sub.2 stored in the memory part M3. When this idle/busy information represents idle, the switching center 30 reads out the terminal number of a terminating terminal of a terminating subscriber stored in the terminating terminal memory part M2 and performs an outgoing call connection process.Type: GrantFiled: March 14, 1996Date of Patent: December 30, 1997Assignee: NTT Mobile Communications Network, Inc.Inventors: Akihisa Nakajima, Masami Yabusaki, Shoichi Hirata, Kenichi Yamaguchi, Shiokazu Fujiwara, Yasuo Maruyama, Yasuyuki Uchiyama, Eriko Takemoto
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Patent number: 5694388Abstract: A CDMA demodulator which can follow fast fading, and reduce interference components from other users in the same cell. A received input spread signal is despread by an orthogonal filer (103). The orthogonal filer provides the input spread signal with successive delays each of an amount of 1/m of the chip interval of a spreading code, multiplies the delayed signals by tap coefficients, and sums up the products, thereby outputting the despread signal. Pilot symbols in the despread signal are compared with known pattern pilot symbols by an absolute phase estimator/phase error compensator (107) to obtain phase fluctuations of the received pilot symbols. The phase fluctuations are interpolated to each information symbol, and each information symbol is phase compensated. The phase compensated information symbols are decided by a decision block (108).Type: GrantFiled: November 22, 1995Date of Patent: December 2, 1997Assignee: NTT Mobile Communications Network Inc.Inventors: Mamoru Sawahashi, Hidehiro Andou, Fumiyuki Adachi
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Patent number: 5692015Abstract: A coherent detection method including a step of estimating a transfer function of a propagation path using pseudo-pilot signals which consist of some information symbols adjacent to pilot signals. The information symbols in the pseudo-pilot signals are assumed to be known. The method includes the steps of estimating the transfer functions using the pilot signals, carrying out interpolation coherent detection of the information symbols using the estimated transfer functions, storing the detection results as the pseudo-pilot signals, reestimating the transfer functions associated with the information symbols corresponding to the pseudo-pilot signals by using the pseudo-pilot signals and the corresponding received signal under the assumption that the pseudo-pilot signals have a known correct pattern, and carrying out the interpolation coherent detection of the individual information symbols by using the transfer functions obtained by the reestimation.Type: GrantFiled: November 28, 1995Date of Patent: November 25, 1997Assignee: NTT Mobile Communications Network, Inc.Inventors: Akihiro Higashi, Fumiyuki Adachi, Koji Ohno, Mamoru Sawahashi
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Patent number: 5689355Abstract: A repeater which is installed as measures for silent zones, which automatically compensates for a variation in a light loss caused by a difference in length among optical cables interconnecting a master device and a plurality of slave devices which are allocated and installed in an underground shopping center or the like. The master device and the slaves devices both have current detectors for detecting current values of O/E transducers which transduce received lights to electric signals. Based on the detected current values, gain control signals are applied to variable gain amplifiers to change their amplification factors so that the levels of output RF signals for transmission to a radio base station and a portable station have a prescribed value, thereby compensating for the variation in the light loss of the optical cables. The present invention greatly facilitates the installation of the repeater and additional installation of slave devices.Type: GrantFiled: July 1, 1996Date of Patent: November 18, 1997Assignees: Kokusai Electric Co., Ltd., NTT Mobile Communications Network Inc.Inventors: Yoichi Okubo, Michio Norichika, Takashi Yokote, Hiroshi Suzuki, Tadashi Akiyama, Jun Suganuma
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Patent number: 5689503Abstract: When data is transferred by using a plurality of time slots, the transferring period is shortened by adopting priority to assign the required number of slots. The base station BS which accepted packet P1 generates a "BUSY" signal and an echo at the final portion of the first time slot TS which begins at time t4. The base station BS, recognizing that there is a packet following the packet P1, generates a "RESERVED" signal at the final portion of the time slot TS which begins at time t5. The mobile station MS-A learns that the first time slot is assigned by recognizing the "BUSY" signal and the echo, and that the second time slot is also assigned by recognizing the "RESERVED" signal. Therefore, the first and second time slots are used successively for fast transferring.Type: GrantFiled: November 16, 1995Date of Patent: November 18, 1997Assignee: NTT Mobile Communications Network Inc.Inventors: Azusa Wada, Akihiro Maebara, Ichiro Okajima, Katsumi Kobayashi, Noriko Uchida, Shinji Uebayashi, Narumi Umeda
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Patent number: 5686926Abstract: Two beams with equiangular spacing are formed at a single antenna face, and multiple beams are generated by combining a plurality of such faces. This makes it possible to reduce the size of an antenna device and to decrease the wind load sustained by an antenna, whereby it becomes possible to mount many antennas on a single supporting structure and to achieve substantial weight reduction of a supporting structure.Type: GrantFiled: September 11, 1996Date of Patent: November 11, 1997Assignee: NTT Mobile Communications Network Inc.Inventors: Makoto Kijima, Yoshihide Yamada, Yoshio Ebine, Minoru Kuramoto
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Patent number: 5677954Abstract: When an incoming call corresponding to a communication number PID takes place in a switching station, the switching station retrieves user-intrinsic information UK and an incoming-communication registered terminal identification number SID and sends the communication number PID to a communication terminal. When the communication terminal replies, the switching station generates a random number R and sends it to the communication terminal. In addition, the switching station generates a cryptical key K=F (R, UK) corresponding to the user-intrinsic information UK and the random number R. The communication terminal generates a cryptical key K=F (R, UK) corresponding to the received random number R and the user-intrinsic information UK that is input by the user. The switching station and the communication terminal encrypt the communication information corresponding to the cryptical key K and decrypt received encrypted communication information.Type: GrantFiled: January 12, 1995Date of Patent: October 14, 1997Assignee: NTT Mobile Communications Network, Inc.Inventors: Shoichi Hirata, Yasuyuki Uchiyama, Hiroshi Tsukahara, Masami Yabusaki
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Patent number: 5673260Abstract: CDMA mobile communication method and system for realizing an autonomous distributed control of radio channel allocation, a synchronization control for a smooth establishment/switching, and a VOX control for a capacity increase are provided. At either one station of each base station and the mobile station, one of a plurality of prescribed short spread codes is selected, and a data sequence to be transmitted is spread by using the selected short spread code and a prescribed long spread code and then transmitted, while at another one station, the data sequence before spreading is reproduced and received by despreading the data sequence from that either one station by using the selected short spread code and the prescribed long spread code.Type: GrantFiled: October 5, 1995Date of Patent: September 30, 1997Assignee: NTT Mobile Communications Network Inc.Inventors: Narumi Umeda, Akihiro Higashi, Akira Hiroike, Akira Kaiyama
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Patent number: 5666655Abstract: A mobile communication system using an autonomous distributed type dynamic channel allocation scheme, in which each base station manages allocation priority levels for the available radio channels according to past records of channel use for each radio channel, and updates the allocation priority level of each radio channel by weighting past allocation accept/reject judgement results for each radio channel with weight factors which vary according to time intervals of the past allocation accept/reject judgement results from a current time. The mobile stations can be grouped into N groups according to states of the mobile stations and N sets of allocation priority levels for each radio channel in correspondence to these N groups can be managed at each base station. The thresholds for grouping the mobile stations can be determined according to past records of states of the mobile stations.Type: GrantFiled: February 2, 1995Date of Patent: September 9, 1997Assignee: NTT Mobile Communication Network Inc.Inventors: Yoshihiro Ishikawa, Narumi Umeda
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Patent number: 5654667Abstract: In a reference signal adaptive estimation part 15, a received signal sample z.sub.n-2 at time (n-2) is phase rotated by M states .DELTA..phi..sub.n-1 at time (n-1), and the phase-rotated signal and a received signal sample z.sub.n-1 are used to calculate the following linearly predicted value of the received signal sample at time (n-1) that contains a fading variation at time n,z.sub.n-1 =(1+.lambda.)z.sub.n-1 -.lambda.z.sub.n-2 exp(j.DELTA..phi..sub.n-1).A square error between a signal phase-rotated .DELTA..phi..sub.n from the linearly predicted value z.sub.n-1 and a received signal sample z.sub.n is calculated as a branch metric in a branch metric calculating part 16 and this branch metric is used for decoding in a Viterbi decoding part 17. A prediction coefficient .lambda.Type: GrantFiled: February 22, 1996Date of Patent: August 5, 1997Assignee: NTT Mobile Communications Network, Inc.Inventor: Fumiyuki Adachi
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Patent number: 5652765Abstract: A repeater improving the effect of a RAKE reception. A received signal from a base station parallelly passes a first path including a first delay circuit and a second path including no delay circuit, and is transmitted to a mobile station. A received signal from the mobile station parallelly passes a third path including a second delay circuit and a fourth path including no delay circuit, and is transmitted to the base station. The delay time of the delay circuits are set at one chip interval or more of a spreading code. This forcedly produces multipath waves which are resolvable by a RAKE receiver. The RAKE receiver estimates amplitudes of desired wave components for individual delayed waves, performs weighting of the respective delayed wave components from detectors by using the estimated amplitudes, and makes symbol decision in terms of the combined weighted signal.Type: GrantFiled: May 22, 1995Date of Patent: July 29, 1997Assignee: NTT Mobile Communications Network Inc.Inventors: Fumiyuki Adachi, Mamoru Sawahashi, Akihiro Higashi, Koji Ohno, Tomohiro Dohi
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Patent number: 5649301Abstract: In a mobile communication network, a mobile unit location register ML and a subscriber location register SL are provided. In the mobile unit location register the mobile location of a mobile unit MT is registered, whereas in the subscriber location register a mobile unit MT selected by each subscriber SB as a terminal for call terminating use is registered. Upon receiving a terminating call for a subscriber, a switching center SW reads out, from the subscriber location register SL, an identifying number TID of the mobile unit registered by the subscriber SB as a terminal for call terminating use and uses the mobile unit identifying number TID to read out the mobile location of the mobile unit MT from the mobile unit location register ML, thereafter sending the terminating call to the registered mobile unit of the read-out mobile location.Type: GrantFiled: June 17, 1994Date of Patent: July 15, 1997Assignee: NTT Mobile Communications Network, Inc.Inventors: Masami Yabusaki, Yasuo Maruyama, Shoichi Hirata, Hiroshi Nakamura, Yasuyuki Uchiyama, Hiroshi Tsukahara, Eriko Takemoto
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Patent number: 5638362Abstract: A correlation detector is provided which can establish initial acquisition quickly, and achieve high accuracy tracking by extracting crosscorrelation components in a receiver for CDMA communication, and a communication system using the correlation detector is also provided. During the initial acquisition, a received signal 21 is supplied to a matched filter 43. When an acquisition decision circuit 45 decides that the matched filter 43 detects the acquisition, it controls a switching circuit 42 to supply the received signal 21 to multipliers 47 and 48, and resets a VCCG 29 and a spreading code replica generator 30. After establishing the acquisition, a received spreading code is quasicoherent detected, and the detected spread signal is multiplied by a phase advanced replica and a phase retarded replica. Correlation detection signals are produced from the products, and squared components of the correlation detected signals are generated, summed in the opposite phase, and averaged along the time axis.Type: GrantFiled: June 13, 1995Date of Patent: June 10, 1997Assignee: NTT Mobile Communications Network, Inc.Inventors: Tomohiro Dohi, Mamoru Sawahashi, Fumiyuki Adachi
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Patent number: 5629948Abstract: An ARQ data transmission scheme in which the overhead due to the ARQ control data is reduced to resolve the problem of the throughput deterioration. The error correction code for the original data is used for each re-transmission block or sub-block, and the block or sub-block corresponding to each re-transmission block or sub-block is found by carrying out the error correction operation with respect to each block or sub-block to be re-transmitted which is stored in the memory, so that there is no need to include the block or sub-block number for identifying each block or sub-block in the re-transmission frame, and consequently the ratio of the ARQ control data with respect to the transmission data can be made relatively smaller and the throughput can be improved.Type: GrantFiled: July 22, 1994Date of Patent: May 13, 1997Assignee: NTT Mobile Communications Network Inc.Inventors: Junichirou Hagiwara, Kouichi Sawai, Shinji Uebayashi
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Patent number: 5623486Abstract: A transmission power control method is disclosed for controlling transmission power of radio communications in a CDMA system. The transmission power of a first transmitted signal transmitted from a first station is determined by a transmission power control signal contained in a second transmitted signal sent from a second station. The first station receives the second transmitted signal in the form of convolutional codes, and decodes it by using a first Viterbi decoder and a second Viterbi decoder. The first and second Viterbi decoders includes path memories with the path history length of different first predetermined lengths. The transmission power control signal contained in the second transmitted signal is extracted from the output of the second Viterbi decoder, whereas the other information data is obtained from the output of the first Viterbi decoder. The first station controls the transmission power of the first transmitted signal on the basis of the extracted transmission power control signal.Type: GrantFiled: May 17, 1995Date of Patent: April 22, 1997Assignee: NTT Mobile Communication Network Inc.Inventors: Tomohiro Dohi, Mamoru Sawahashi, Koji Ohno
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Patent number: 5619167Abstract: A received signal sample sequence is inversely modulated by a symbol sequence forming the trellis state at the immediately preceding time, by which a reference signal is generated. This reference signal and the inner product of the received signal sample at the current time and a candidate symbol phase are used as a branch metric to make a sequence estimation by the Viterbi algorithm.Type: GrantFiled: December 22, 1995Date of Patent: April 8, 1997Assignee: NTT Mobile Communications Network, Inc.Inventor: Fumiyuki Adachi